This invention relates generally to cathode-ray tubes having tension mask assemblies and, more particularly, to tension mask assemblies having vibration damping means.
A color cathode ray tube, or CRT, includes an electron gun for forming and directing three electron beams to a screen of the tube. The screen is located on the inner surface of the faceplate panel of the tube and is made up of an array of elements of three different color-emitting phosphors. A shadow mask, which may be either a formed mask or a tension mask having strands, is located between the electron gun and the screen. The electron beams emitted from the electron gun pass through apertures in the shadow mask and strike the screen causing the phosphors to emit light so that an image is displayed on the viewing surface of the faceplate panel.
One type of CRT has a tension mask comprising a set of strands that are tensioned onto a mask support frame to reduce their propensity to vibrate at large amplitudes under external excitation. Such vibrations would cause gross electron beam misregister on the screen and would result in objectionable image anomalies to the viewer of the CRT.
Vibrations causing gross electron beam misregister may be created by microphonic sources within the TV set. Although it is difficult to control the amount of vibration generated by these microphonic sources, it is necessary to have the tension mask within the CRT be adaptable to this environment in which such microphonic vibrations exist. While tensioning the mask strands reduces electron beam misregister, further reductions are necessary. It is therefore desirable to develop a mask frame assembly having vibration damping characteristics for further minimizing the undesirable result of electron beam misregister on the screen caused by vibration sources within the TV set.
A cathode-ray tube having a luminescent screen on a faceplate panel and a tension mask assembly, wherein the assembly comprises a pair of support blades for supporting a tension mask. The tension mask has a pair of mask borders each being fixed to a respective support blade and a plurality of strands extending between the mask borders. The mask further comprises cross wires extending generally perpendicular to the strands on a screen facing side and at least one shield assembly extending between and attached to the mask borders. The shield assembly has a sheath extending along one side of the mask in contact with at least one strand and a shield attached to the cross wires of the mask in overlapping relation to the sheath.